Pt-S Bond-Mediated Nanoflares for High-Fidelity Intracellular Applications by Avoiding Thiol Cleavage

Rapid Capture and Photocatalytic Inactivation of Target Cells from Whole Blood by Rotating Janus Nanotubes

Effective isolation and removal of target tumor cells from patients' peripheral blood are of great importance to clinical prognosis and recovery. However, the extremely low quantity of target cells in peripheral blood becomes one of the challenges in this respect. Herein, we design and synthesize an innovative nanostructure based on magnetic TiO₂ nanotubes with Pt nanoparticles' asymmetrical decoration for effectively capturing and inactivating target cells. Using CCRF-CEM as the model cell, the resulting nanotubes with accurate modification of recognition probes exhibit high selectivity and cell-isolation efficiency upon real blood samples. Particularly, the target cells are selectively captured at a low concentration with a recovery rate of 73.0 ± 11.5% at five cells per milliliter for whole blood samples. Consequently, benefitting from the remarkable photocatalytic activity of the Janus nanotubes, these isolated cells can be rapidly inactivated via light-emitting diode (LED) irradiation with an ignorable effect on normal cells. This work offers a new paradigm for high-efficient isolating/killing target cells from a complex medium.

Establishment of Dual Hairpin Ligation-Induced Isothermal Amplification for Universal, Accurate, and Flexible Nucleic Acid Detection

Isothermal amplifications have found their potentials in applications of portable nucleic acid diagnostics. However, there are still several certain deficiencies existing in the current amplification methods, including high false-positive signals, limited range of targets, difficult primer design, and so forth. Here, we report an effective solution via the development of dual hairpin ligation-induced isothermal amplification (DHLA) consisting of (1) the formation of a dual hairpin probe (DHP) based on sequence specific hybridization and ligation and (2) exponential isothermal amplification of DHP in the presence of polymerase and primers. Taking both microRNA and virus RNA as model targets, DHLA is proven to be accurate, flexible, and applicable to most deoxyribonucleic acid and ribonucleic acid targets ranging from ∼20 to hundreds of nt. The detection limit is down to the ∼aM level without a false-positive signal. More importantly, the whole detection can be directly applied to a new target via a slight change in the DHP sequence, without redesigning the primer set. This unique property not only simplifies the process for new reaction development but also enables flexible multiprobe strategies to achieve antidegradation analysis.

Enhancing the peroxidase-like activity and stability of gold nanoparticles by coating a partial iron phosphate shell

Using citrate-capped gold nanoparticles (AuNPs) as peroxidase-mimicking enzymes to design biosensors is hindered by their low catalytic activity and poor colloidal stability, resulting in limited sensitivity and large variations. Herein, the growth of a partial iron phosphate (FeP) shell with Fe²⁺ ions on citrate-capped AuNPs boosted the activity of the AuNPs by up to 20-fold. The FeP-enhanced activity was demonstrated on AuNPs of different sizes, and gold nanostars. When the FeP layer is thick enough to block the access to the Au/FeP interface, the activity was inhibited. Capping the remaining Au surface by thiol also inhibited the activity, suggesting that faster reactions occurred at the interfaces of Au/FeP. Moreover, a FeP shell can stabilize AuNPs against freezing and a high NaCl concentration of 1 M. Sensitive detection of Fe²⁺ was achieved with a detection limit of 0.41 μM, while no other tested transition metal phosphates enhanced the peroxidase-like activity of AuNPs.

Promoting DNA Adsorption by Acids and Polyvalent Cations: Beyond Charge Screening

Adsorbing DNA oligonucleotides onto nanoparticles is the first step in developing DNA-based biosensors, drug delivery systems, and smart materials. Since DNA is a polyanion, it is repelled by negatively charged nanoparticles, which constitute the majority of commonly used nanomaterials. Adding salt such as NaCl to screen charge repulsion is a standard method of promoting DNA adsorption. However, Na⁺ does not supply additional attractive forces. In addition, adding a high concentration of NaCl can cause the aggregation of nanomaterials. In this feature article, we mainly summarize the methods developed in our laboratory to promote DNA adsorption by lowering the pH and by adding polyvalent metal ions, especially transition-metal ions. Various materials including noble metals (gold, silver, and platinum), 2D materials (graphene oxide, MoS₂, WS₂, and MXene), polydopamine, and several metal oxides are discussed. In general, low pH can protonate DNA bases and nanoparticle surfaces, reducing charge repulsion and even leading to attraction, although DNA folding at low pH can sometimes be detrimental to adsorption. Polyvalent metal ions can bridge additional interactions to achieve otherwise impossible adsorption. On the basis of the current understanding, a few future research directions are proposed to further improve DNA adsorption.

DNAzyme–gold nanoparticle-based probes for biosensing and bioimaging

The design and applications of DNAzyme–gold nanoparticle-based probes in biosensing and bioimaging are summarized here.